1. Field of the Invention
This invention relates to a probe card, especially to a probe card to connect electrically between semiconductor measuring apparatus and IC pads.
2. Description of the Prior Art
In the manufacturing process of semiconductor integrated circuit, after the end of diffusion process, by semiconductor measuring apparatus (tester), the electrical characteristics are measured in the state of wafer. In this tester, as a board to connect electrically IC pads (electrodes) with the tester itself, a probe card is provided. The probe needles furnished in this probe card are contacted to IC pads in order to connect to IC electrically.
The conventional probe card is comprised of printed circuit board, probe needles, resin to fix needles, upper guide plate, lower guide plate and fixing frame. A print circuit board connects probe needle to the measurement device itself electrically. The top end of probe needle is connected to wirings on the print circuit board with soldering. The lower end of the probe needle is the tip to touch a pad. At the center of probe needle, there is a curving part to buffer contact pressure toward the pad. Resin to fix needles fixes probe needle under the print circuit board. The upper and lower guide plates guide probe needles by guide holes to pass through probe needles. The fixing frame is fixed to the print circuit board and fixes the needle-fixing resin and the upper and lower guide plates parallel to the print circuit board.
When the wafer is measured, moving the wafer stage within its plane, after the position and the direction are fitted, the stage is lifted to contact the tip of the probe needle to the pad on the surface of the wafer. But the electrical resistance of the contact is large because natural oxide film sticks to the surface of the pad as the wafer is exposed in the atmosphere. It is necessary to expose the metallic surface of the pad in order to connect the probe needle electrically to the pad breaking through the natural oxide film by the probe needle. Therefore, after contacting the pad with probe needle once by raising the stage, furthermore, the stage is raised again. In this way, electrical contact is satisfied because the oxide film on the surface of the pad is scraped by probe needle.
By the way, there are two types of probe card. The probe card of the first type is of the cantilever type, wherein the probe needle comes out of the baseboard in the side oblique direction. The probe card of the second type is of the vertical needle type, wherein the probe needle comes out of the baseboard in the vertical direction. In the case of the cantilever type, probe needle can scrape an oxide film easily sliding on the pad according to the rise of the stage because the probe needle comes out of the board obliquely. In the case of the vertical needle type, contact defect is often caused because the oxide film stuck to the surface of the pad cannot be removed. The probe needle hardly slides on the pad as the probe needle contacts vertically to the pad. In order to solve this problem, in “Semiconductor device measurement device” disclosed in the U.S. patent application 2001-0028255, the oxide film stuck to the surface of the pad is removed by turning probe needles.
As shown in FIG. 9, in this semiconductor measuring apparatus, the rotating guide plate 3 of insulator is arranged between the upper guide plate 2 and the lower guide plate 4. The driving device 6 moves the rotating guide plate 3. The curving part 13 of each probe needle 5 is rotated to the fixed direction through the guide hole 12 of the rotating guide plate 3. As shown in FIG. 9(a), the driving device 6 holds the both ends of the rotating guide plate 3 by the arm. When to drive, as shown in FIG. 9(b), receiving electric signal, the driving device 6 moves the rotating guide plate 3 as the guide hole 12 revolves around the axis of the probe needle 5. In this way, the curving part 13 of the probe needle 5 inserted in the guide hole 12 of the rotating guide plate 3 is forced to revolve centering the axis of the probe needle 5. As the result, the lower top of the needle rotates on the pad 10 and contacts to the pad 10 breaking through the natural oxide film stuck on the surface of the pad.
However, in the conventional probe card, there is a problem that the pad and vamp are unnecessarily damaged. Dispersions of height and position surely exist in probe needle. Dispersions of the form and the movement are easily caused because the probe needle is processed to be a spring. Therefore, some probe needle applies unnecessarily strong force to the pad, some probe needle applies only minimum necessary force to the pad. The strong probe needle injures the pad with the strong force. And also there is a problem that assembling is difficult in the case of the probe needle being rotated with the curving part in the center. The pitch of the probe needles is restricted by the size of the curving part. Such probe card cannot be applied to the narrow pitch pad.
The object of the present invention is to enable the measurement of integrated circuit without damage larger than the needle diameter on the pad by contacting the probe needle to the pad of wafer with the uniform needle pressure in the probe card of semiconductor measuring apparatus by solving the above-mentioned problems of the last.
To solve the above-mentioned problem, in the present invention, the probe card is comprised as follows: an electrically-conductive linear probe needle whose bottom end contacts with the device under test, a circuit board with which the upper end of the probe needle is connected electrically, an upper guide plate held horizontally and firmly near the middle point between the upper end and the center of said probe needle and having a guide hole to guide said probe needle, a lower guide plate held horizontally and firmly near the middle point between the center and the bottom end of said prove needle and having a guide hole to guide said probe needle, a rotary guide plate held horizontally and movably near the center of said probe needle and having a guide hole to guide said probe needle, an initial-position holding means to hold said rotary guide plate temporary and firmly at the initial position where said probe needle is straight, a movable holding means to hold movably said rotary guide plate at the position where the center of said probe needle bent, a driving means to move said rotary guide plate in the horizontal plane.
Measurement can be done without damage larger than the needle diameter on the pad of wafer by preventing the dispersion of the pressure of probe needle. The probe card can be applied to the integrated circuit of narrow pitch pad as the probe needle is straight. Assembling of the probe card becomes easy.